(a) Field of the Invention
The present invention relates to a composition for use in the production of naturally-degradable polymer products which preferably comprises polycaprolactone (PCL), malic acid (MA) and polyethylene glycol (PG). The present invention also relates to a method for producing a composition in the form of tablets for use in the production of naturally-degradable polymer products.
(b) Description of Prior Art
Plastics are being used virtually everywhere and have become an almost indispensable part of everyday life. Some are permanent objects, intended for a long-term use. Others, actually a major portion of plastics population, are found as short-term or single-use articles and include bags, wrappings, containers, bottles, pens, etc. The extensive use of plastics therefore leads to the consequence that plastic residues are found all over the planet, potentially harming wildlife and littering the remotest places.
The majority of ordinary plastic products will remain for centuries or more, since they are composed of huge and unbreakable molecular polymer chains. Indeed, the plastic transformation industries traditionally use, as primary matter, mixtures of extruded plastics chips with additives, which are transformed in objects, such as bags, films, bottles, containers, etc. through blowing, extrusion, milling or injection (these mixtures have been homogenized through heating and extrusion).
To minimize the problems of pollution by plastics, recycling of all plastic products would be ideal. However, such a complete recycling of plastic material is difficult to achieve, since recycling facilities are not available everywhere or are too remote and the population compliance too poor to be cost effective. Then emerges a need to find biodegradable substitutes.
Biodegradable plastic substitutes (BPS) are substances that can be used as conventional plastics, while decomposing on disposal into water and carbon dioxide, by the action of microorganisms commonly present in the natural environment. The BPS can therefore be returned to nature since they would decompose quickly and do not adversely affect the quality of the compost produced in composting facilities.
BPS known in the prior art are natural biopolymers, modified biopolymers or chemically synthesized polymers, and include poly 3-hydroxybutyrate, modified starch, cellulose acetate polybutylenesuccinate, polybutylenesuccinate/adipate, polycaprolactone, polylactic acid and polyvinyl alcohol. These compounds and many other propositions of the industry are actually not fully satisfying plastic substitutes, either because of their poor strength, poor compliance with existing transforming devices, or because they actually are bio-fragmentable—in a myriad of tiny plastic parts or powder-instead of being biodegradable. Polylactic acid derivatives and polyhydroxybuturates are very expensive and their use is therefore restricted mainly to medical purposes, such as resorbable sutures. Polyvinyl acid is decomposed only by water and is used mainly in washing machines detergent pouches. Polytetramethyleneadipate, polybutyleneadipate and polycaprolactone modified with starch-based polymer (Mater-BI) are appropriate for producing films and bags, but not for products obtained by plastic injection. Propositions derived from maize and starch alone may have poor physical qualities and appear to easily clog existing transforming machines. The existing BPS do not meet the requirements for plastic injection and the time required for the degradation of these existing products cannot be adjusted to consumers' needs.
A solution proposed to alleviate the above-described problems related to BPS, consists in the use of BPS mixes. Indeed, the use of a biodegradable polymer combination could enhance the chemical and physical properties of the product produced therefrom. BPS mixes should likely be required to have a granular or chip-like form, since the use of a powder mix is not convenient for the plastic industry machinery, that requires granular or pelletized materbatch. However, mixtures of powders having a wide range of molecular, such as those required in the composition of optimal BPS mixtures, do not tend to produce an homogenous product. Moreover, BPS are not easily pelletized by conventional extrusion process of the plastic industry, since this process requires high temperatures and BPS are, for the majority, not thermostable nor thermoresistant to such extrusion high temperatures.
Therefore, it would be highly desirable to be provided with a method for producing a masterbatch that avoid conventional extrusion while leading to a composition of totally biodegradable BPS, having physical characteristics similar to those of traditional masterbatches, and capable of being transformed by the same industrial equipment. It would also be highly desirable to be provided with a BPS composition at a reasonable cost, and giving an homogenous product, that can be stocked for an extended period time and have a range of degradation time according to specific needs.